The present invention relates to a method and apparatus for decontaminating structures and, more particularly, to an apparatus which projects a non-hazardous abrasive onto the surface of a contaminated structure at a velocity sufficient to remove a layer of the base material from the structure and which immediately reclaims the abrasive material projected onto the structure and the base material removed from the structure.
A major problem now exists in this country with respect to the reuse of sites which were once used to store hazardous materials. The costs associated with remediating these sites can be astronomical. Moreover, once such sites have been remediated, they still may not be suitable for other uses. The Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) generally governs the cleanup of hazardous sites which have been ranked among the most dangerous sites in the country by the Environmental Protection Agency (EPA). These sites are placed on the national priorities list to ensure that they are among the first to be remediated. After a particular site has been listed, the EPA (usually in conjunction with the state where the site is located) determines the type of remediation to be used. In determining what type of remediation is to be used, the EPA looks at several different alternatives and selects the best one based on the consideration of nine criteria: (1) overall protection of human health and the environment; (2) compliance with or waiver of applicable or relevant and appropriate other environmental laws; (3) long-term permanence and effectiveness; (4) reduction of toxicity, mobility, or volume through treatment; (5) short-term effectiveness; (6) implementability; (7) cost; (8) acceptance of the proposed plan by the state; and (9) acceptance of the proposed plan by the affected community.
Although cost is one of the nine criteria considered in selecting a remedial plan, cost usually does not play a major role in the selection and the importance of the other criteria is emphasized. Therefore, it is important to provide a means by which a site, or a particular aspect thereof, can be remediated which meets these criteria and which is cost effective.
Until the present invention, there has been no suitable means for decontaminating structures, such as buildings, which were once used to store or treat hazardous materials. The present invention provides an apparatus which utilizes abrasive blasting effectuated by a nozzle encompassed in a vacuum envelope which allows a layer of the base material of a structure (e.g., a wall, ceiling or floor) to be removed and immediately reclaimed in the vacuum envelope. The abrasive material to be used is preferably non-hazardous and is reclaimed with the removed base material in the vacuum envelope. By immediately reclaiming the abrasive and the removed base material, the need for a secondary cleanup is eliminated or minimized.
In accordance with the present invention, the abrasive material to be used is preferable dry ice. Dry ice is a non-hazardous substance, which results in reduction of the volume of the end product needed to be treated. Also, dry ice has the abrasive characteristics necessary to effectuate removal of a layer of the base material. Although dry ice has been used in other industries as an abrasive, its particular suitability for remediation, in conjunction with the concepts of the present invention, has not until now been proposed.
It has been known in the industry to use devices which decontaminate structures (e.g., removal of lead-based paint) by utilizing pneumatically operated cutting needles encompassed within a stainless steel enclosure. The device is used in combination with a vacuum. The stainless steel enclosure is designed to prevent the release of dust, debris and airborne contamination into the environment. A shroud which is provided on the end of the device helps to direct the reverse airflow created by the vacuum so that debris removed from the structure is immediately collected. However, such a device is generally not suitable for the removal of particular types radioactive material, such as those characterized by neutron activity which may result in the collected material approaching critical mass. One of the primary objects of the present invention is to provide detection means in the vacuum which will warn of neutron activity indicating that the possibility of critical mass is approaching.
Abrasive blasting has also been used in the industry for decontaminating structures. However, open abrasive blasting operations generate dispersions which may be harmful to the operator and others in the surrounding area. Containment structures have been used in conjunction with abrasive blasting. However, such structures require the operator to be located within the containment area while blasting the surface, which may produce adverse health consequences to the operator such a device is generally not suitable for decontaminating structures contaminated with high levels of particular types of radioactive material.
It is also known in the industry to use super-heated water in combination with a spray vacuum to decontaminate surfaces. The super-heated water is in liquid state as it strikes the surface. The impact and temperature of the water cleans the surface and the vacuum collects the water and the material removed from the surface. The present invention proposes the removal of not only the contaminated material from a structure but also the removal of a layer of the base material of the structure itself. A layer of base material should be removed as well as the contaminant due to migration of the contaminant into the base material. The use of super-heated water does not result in removal of a layer of the base material and therefore, will not be suitable for removal of particular types of contaminants.
Therefore, a need exists in the industry for a decontamination device which utilizes abrasive blasting and which is capable of removing hazardous contaminants, such as radioactive contaminants, from structures and immediately reclaiming the contaminants as well as the abrasive.